[Rheo]

Hello CFD users,

I would like to get information about the velocity field in a specific area of a computation domain (not the whole domain) at runtime.

How can I do this?

I am using a polar (2D) grid with physical coordinates. I found out that the ordering of the output form of the U,p,etc files for a polar grid is in the form

(while assuming
i -> r in the range say [0,N]
j -> phi in the range say [0,M]
)

Data[i=0,j=0 to M] with Data a matrix with M lines and three rows
Data[i=1,j=0 to M]
...
Data[i=N,j=0 to M]

I can handle this in the post processing and for a spherical symmetry, but, I know that at runtime, it should be possible to specify a specific area of the mesh by a patch name and use this data. Unfortunately I figured out that this approach is not working for my goals.
I am in addition not interested in the x and y component of the flow, I would like the measure the phi velocity at runtime only.)

So how can I get the physical information (say velocity) by means of any other mapping (like a probe of openFOAMs post processing tools) for a big bunch of cells out of the domain?

Many thanks to you, who are more skilled than me.